The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
An airplane is moved by several jet engines each housed in a nacelle serving to channel the flows of air created by the jet engine that also houses a set of actuating devices performing various functions, when the jet engine is running or stopped.
These actuating devices may in particular comprise a mechanical thrust reversal system.
The nacelle generally has a tubular structure comprising an air intake upstream from the jet engine, a middle section designed to surround a fan of the jet engine, and a downstream section housing thrust reversal means and designed to surround the combustion chamber of the jet engine, and generally ends with a jet nozzle whereof the outlet is situated downstream from the jet engine.
Modern nacelles are designed to house a dual flow jet engine capable of creating, through the blades of the fan, a flow of air whereof one portion, called hot or primary flow, circulates in the combustion chamber of the jet engine, and the other portion of which, called cold or secondary flow, circulates outside the jet engine through an annular passage, also called a tunnel, formed between the fairings of the jet engine and the inner walls of the nacelle. The two flows of air are ejected from the jet engine through the rear of the nacelle.
The role of a thrust reverser is, during landing of an airplane, to improve the braking capacity thereof by reorienting at least part of the thrust created by the jet engine forward. In this phase, the reverser obstructs the cold flow tunnel and orients that flow toward the front of the nacelle, thereby creating a counter-thrust that is added to the braking of the wheels of the airplane.
The means used to perform this reorientation of the cold flow vary depending on the type of reverser. However, in all cases, the structure of a reverser comprises movable cowls that can be moved between a closed or “direct jet” position, in which they close said passage, and an open or “reverse jet” position, in which they open a passage intended for the deflected flow in the nacelle. These cowls may perform a deflection function or simply serve to activate other deflecting means.
In the case of a grid reverser, also called a cascade thrust reverser, the flow of air is reoriented by cascade vanes, the cowl serving only to slide so as to expose or cover said vanes.
The moving cowl is translated along a longitudinal axis substantially parallel to the axis of the nacelle. Optionally, thrust reverser flaps, actuated by the sliding of the cowl, allow obstruction of the cold flow tunnel downstream from the cascade vanes, so as to optimize the reorientation of the cold flow toward the outside of the nacelle.
Known from the prior art, and in particular from document FR 2,916,426, is a grid reverser whereof the moving cowl is a single piece and slidably mounted on guideways positioned on either side of the suspension pylon for the assembly formed by the jet engine and its nacelle.
“Single-piece cowl” refers to a quasi-annular cowl extending from one side of the pylon to the other without interruption.
Such a cowl is often referred to as an “O-duct”, referring to the shroud shape of such a cowl, as opposed to a “D-duct”, which in fact comprises two half-cowls each extending over a half-circumference of the nacelle.
The sliding of an O-duct cowl between its “direct jet” and “reverse jet” positions is traditionally done by a plurality of actuators, for example of the mechanical-electrical or hydraulic type, for example.
Typically, there are four or six actuators, i.e., respectively two or three actuators distributed on each half of the thrust reverser, on either side of the suspension pylon and mounted on the front frame of the thrust reverser.
To bear the forces transmitted by said actuators, it is in particular possible to provide reinforcing structures, for example at the fastenings of the cylinders on the moving cowl, such as the presence of fittings, the use of thickened composite panels and more dense sandwich structure cores.
However, these structures make the thrust reverser heavier.
Such an assembly is also faced with other drawbacks.
Thus, grouping the actuators together in the upper part of the circumference of the thrust reverser risks posing difficulties resulting from the tilting torques created by the forces generated by said actuators during opening and closing of the cowl.
This position of the cylinders may generate jamming phenomena in the sliding rails of the cowl, due to their circumferential offset relative to said rails.